After spending the last month diagnosing and basically firing the parts cannon at my ‘92 T/A 305 TPI, this is a PSA for anyone who may be experiencing similar issues and is in the process of pulling out their hair one day at a time. Suddenly, after having zero reliability or driveability issues with this car, it left me stranded after having lunch one day. The symptoms: it wouldn’t start, and the SES light was randomly flickering (not flashing) with the key “on.” Starter would crank, I could hear the fuel pump whine, and it would fire off momentarily, but sputter and die. While having lunch, the temperature had dropped a bit and it had started raining.

I called an Uber to get home, came back later to retrieve the car, and it fired right up, drove home 30 min with zero issues. But the pattern had just begun. Every day for the next few weeks (Spring in Southern VA), the car would occasionally not start, same symptoms. But later on, it might start and run just fine. I replaced the ICM, Coil, Distributor, Plugs, Wires, Fuel Filter, Fuel Pump, EGR solenoid, and even bought a 2nd ECM for trouble shooting purposes- nothing solved the random SES flickering/no-start/sputtering issue. Until one evening, in pure desperation, I had swapped back in my original ECM and pushed the MEMCAL chip in to notice that, if I left my thumb on the chip, the SES flicker, and all of the symptoms went away!

I took the MEMCAL inside, set it on the bathroom countertop, and sure enough- the plastic housing where it seats into the ECM was concave. So, in cold weather, without the pressure of my thumb pressing it in down, it was lifting away from the pins just enough to cause a random no-start/sputter issue.

I’m posting this because I can’t be the only one having experienced this problem, and it nearly drove me to swap over to a carburetor (I have and ‘81 T/A with a 383 stroker and HEI/Carb setup, so I was just gonna mimic that on the little 305). These old plastic chip housings may have warped over the years (mine spent 30 yrs in Phoenix, AZ before I bought it), and they can wreak havoc in an otherwise gem of a car. If you are having issues similar to mine that you can’t seem to diagnose- CHECK THE PROM/MEMCAL chip!

The fix- I sanded down the edges of the plastic housing with some 80 grit paper so that it would seat flush inside the ECM once again, after apologizing to my wife for the $1,500 or so worth of Summit and O’Reilly’s purchases that led me to the ultimately “free” solution.

This is a pic of my ‘92 T/A’s MEMCAL chip, showing just how much the seating area of the plastic housing has warped (you can see daylight in the middle at the bottom of the housing).

 

I do not own a car like u. Do own a 1984 Firebird Trans AM with a 305 + an old school QJ (canadian export) .
I must commend u for the investigative work that resolved your issues.Something so simple as flattening a surface for full contact.
So simple yet so effective!

 

You need to figure out why it is getting that hot to warp that chip. The ECM is under the dash and shouldn't be getting that warm.

 

Anything made out of plastic is bound to warp and deteriorate a bit when exposed to temps ranging from 0-120 degrees for 3 decades. This particular T/A spent 30+ yrs in AZ before I bought it, I imagine that may have exasperated the issue. I’ve only owned it for 6 months so I’m still looking for any gremlins that may be hiding, but this was one that had me stumped for a solid month!

I had purchased a used PROM/MEMCAL chip on ebay (part of the parts cannon blast) and noticed that IT’S housing was also warped (turned out to be for a V6 so I couldn’t use it anyway). This leads me to suspect that it is more of a widespread issue with our cars and may be overlooked when random no-start issues arise.